1. Field of the Invention
The present invention relates to a battery charger for charging a battery pack having a memory and a secondary battery, and relates to a control method therefor.
2. Description of the Related Art
In a conventional deterioration management of a battery pack having a memory function and a residual capacity indication function, a change in the output voltage of a power source (secondary battery) is detected inside the battery pack, and the number of times the battery pack has been used and the number of times the battery pack has been charged and discharged are counted for storage in a memory (see, for example, Japanese Laid-open Patent Publication No. 08-037036).
In the above-described prior art, a change in the secondary battery voltage is measured inside the battery pack. Therefore, voltage measurement means must be provided inside the battery pack. In addition, a microcomputer must be provided. With this arrangement, the battery pack is complicate in its internal circuit, which increases the cost of the battery pack. Furthermore, a deterioration of the secondary battery occurs, if the battery pack is left unattended. Nevertheless, no countermeasure is taken against the battery deterioration of the secondary battery left unattended in a charged state, which poses a problem. Another problem is that no countermeasure is taken against the battery deterioration due to repeated charge cycles of the battery pack.